YALE (US) — Researchers have found a key component in the mystery of preterm labor, a leading cause of death and permanent disability in newborns.

Excessive formation of calcium crystal deposits in the amniotic fluid may be a reason why some pregnant women suffer preterm premature rupture of the membranes (PPROM) leading to preterm delivery.

The findings were presented recently at the Society for Maternal-Fetal Medicine Scientific Sessions in San Francisco, California.

Infection, maternal stress, and placental bleeding is know to trigger some preterm deliveries, but the cause of many other preterm deliveries is unknown. In these cases, women experience early contractions, cervical dilation, and a torn amniotic sac.

“We noticed that in many women, analysis of the proteins in their amniotic fluid did not show signs of inflammation, and we could not find any cause for their preterm birth,” says Lydia Shook, a medical student working with Irina Buhimschi, associate professor of obstetrics, gynecology, and reproductive sciences at Yale University.

“We took a fresh look for what was causing breakdown of the membranes, which can lead to lost elasticity, integrity, and eventually rupture.”

Scientists know that calcifying nanoparticles are involved in many degenerative conditions including arthritis and atherosclerosis.

“These mineral-protein complexes can disrupt normal cellular processes and cause cell death,” Shook says. “We wondered whether they could also be responsible for damage to the fetal membranes in pregnant women.”

Researchers used a stain to look for calcium deposits in placental and fetal membrane tissue from patients with PPROM and preterm birth, as well as full-term deliveries.

They used a sterile culture technique to determine whether amniotic fluid can form nanoparticles and then exposed fetal membranes to the cultured nanoparticles to determine their ability to induce cell dysfunction, damage, and cell death.

Calcification of fetal membranes collected from preterm deliveries was in evidence—fetuin, one of the major proteins involved in nanoparticle formation, was found in the deposits.

Levels of fetuin in amniotic fluid were lower in women who delivered with PPROM compared to those who delivered early with intact membranes.

“This preliminary evidence suggests that amniotic fluid has the potential to form nanoparticles and deposit them in the fetal membranes,” Shook says.

“Low fetuin may be a biomarker for women at risk of PPROM. The goal of this research is to identify women at risk of developing this condition early in their pregnancy and to intervene with targeted therapy.”